Sir,

Movement of loose stones over bedrock surfaces below a cover of snow, such as described from Mount Twynam (Reference CostinCostin and others, 1964), is characteristic of the area adjacent to the glacier Østerdalsisen, in Norway (lat. 66° 31′ N., long. 14° 06′ E.). Stones are moved down slope on the bare rock which lies between the southern margin of the glacier and the moraine which marks the maximum recent extent of the ice (c. a.d. 1750). Movement between one summer and another is typical.

The stone shown in Figure 1 measured about 20 cm.×6 cm.×4 cm., and the fresh, white abrasion marks up-slope of it were about 25 cm. long on 2 August 1964. The stone had moved approximately down the line of greatest slope (about 24 degrees), oblique to the direction of old striations on the garnet mica schist bedrock. In 1963–64 the maximum snow depth in the area was a bout 170 cm., which is of the same order as the mean of recent years.

Fig. 1. Down-slope movement of stone. Old striations (top) run slightly across the slope; fresh abrasion marks behind the stone run down the line of greatest slope. Photograph taken 2 August 1964

During the winters, many stones a re moved over the bare rock surface bordering Østerdalsisen, though few of them show any definite orientation relative to the slope. There seems no doubt that slow downhill creep of snow may result in abrasion of the underlying rock by loose stones at the bottom of the snow cover.

20 October 1964